Project Corn Star: Tuning An LS For Boost With HP Tuners

Tuning often seems like a dark art to the uninitiated. A few clicks here, a few taps there and voila! The car is running like it was built with those modifications in mind. Seems a little bit like magic, right? Well, the truth is, we were once in that same position. But just like any skill, automotive or otherwise, it can be learned with enough time and patience.

However, as with any skill, it pays to have a good teacher. While it’s likely better to attend a course in person where trained instructors can help you if you ever have a hiccup or question, not everyone is going to be able to afford or even attend a session to learn to tune, much less multiple sessions. But fear not! We have joined forces with the guys over at HP Tuners and The Tuning School to bring you an overview of the steps we took to get Project Corn Star up and running on its new Speed Density tune.

If you’ve been following along with Project Corn Star, you know that we have made some radical modifications to our fourth-gen Camaro. We increased the displacement by way of an iron-block 370 from Blueprint Engines, it’s now running on a corn-based fuel, and it has a relatively large snail strapped to it now.

Needless to say, the changes to our 0411 (P01) computer would be comprehensive. We need to tell it that it’s running a larger motor, using larger injectors, and running without the MAF. Before you go running for the hills tearing your hair out just reading this, we are going to walk you through the steps we took to get Corn Star’s 1s and 0s in line, and that all started with our GM tuning guide from The Tuning School and our interface from the guys at HP Tuners.

The Tuning School

Now, if you’re anything like us, you’ve probably wondered to yourself: “why is tuning so difficult to grasp? After all, the engineers at GM probably have a step-by-step procedure for tuning them in the first place, why not me?” And that is the perfect question to be asking, and the answer to it is—YES! There is absolutely a step-by-step process for it and The Tuning School has outlined it all in its manuals. In fact, they even give you a laminated checklist for tuning, so you don’t miss anything. It then correlates with the sections of the training manual in case you need a little more in-depth information on what you should be doing.

If you’ve investigated tuning at all, you’ve probably spent countless hours scouring the internet looking for one cohesive guide for tuning. You’ve probably found forum pages that promise to walk you through it, but by the end of it all you’re more confused than when you started, and you’ve read at least six pages of people telling each other they are morons and don’t know how to tune. Again, we’ve been there, and when you’re done frustrating yourself pouring over page after page of cobbled together techniques and incomplete information The Tuning School is the perfect place to start. You can attend their classes if you’d like and they have countless online resources, and of course, their manuals, if you are too remote to catch one of their in-person classes or want to take it at your own pace.

While this isn’t our first rodeo with tuning, The Tuning School’s manuals taught us more than a thing or two and organized it into a repeatable format that you can then apply to any vehicle. We will be focusing on the tuning of a Gen III engine, but much of it applies to Gen IV applications, which the manual will walk you through as well. But, without further ado, here are the steps we took to get Corn Star up and running.

But before we get to that, we want to preface this by saying a few things first. This article isn’t a comprehensive guide where we show every parameter we changed and every table we modified (that is what The Tuning Schools guides are for), it is merely a 10,000-foot view of the changes we need to make to get everything up and running. Secondly, this is just a base map to get the car running and driving so we can make sure everything is operating correctly, and our tuner won’t have to spend valuable time getting it up and running to find out something is mechanically wrong.

Interfacing

To get tuning, obviously, you’re going to need some software to start out with. There are several great companies that can help with this but we turned to the guys over at HP Tuners for one of their MPVI Pro systems. This includes both the VCM Editor and VCM Scanner software, which are used to modify the tune and scan the vehicle for live data respectively. You can’t start your tuning quest without something like this, and we will be showing you our steps as they apply in the HP Tuners software.

You can see here that HP Tuners interface allows a laptop to plug right into the OBD-II port of the vehicle. Additionally, we have the signal from our wideband and fuel pressure gauge wired in so we can data log them in real time with the other OBD-II parameters.

Our system came with the interface that allows us to plug our laptop into the vehicle as well as an EIO plug that will allow us to input up to two analog signals and two digital signals that are not gathered by the car’s OBD system. We will use these to log our wideband and other parameters inside the software as it pulls data from the OBD port, but we’ll spend more time on that a little later. Since we received our MPVI Pro, and the credits necessary to tune our Camaro, HP Tuners has released a new interface they are calling the MPVI2. It uses Bluetooth to interface with your laptop and is packed with impressive new features, but we’ll be sticking with our interface for now.

The first order of business now that we had our software in hand was to pull the original tune, so we have something to compare to and revert to in case things go awry. That’s accomplished simply by plugging the interface into the vehicle, pulling up the VCM Editor software, turning the key to the “On” position, and then hitting the “Read Vehicle” button at the top of the software. With our base file read, we can start making modifications.

Getting Started

With our Camaro’s tune now open, it was time to upgrade it to a 3-bar Speed Density tune. This means that we will not be using the MAF sensor and will rely on the MAP sensor, as well as speed and other inputs, to calculate the fueling needs of the engine in any given state. Eliminating the MAF is not necessarily part of adding boost to an LS, but with early generation computers like ours, scaling the MAF signal would cause us to lose important resolution and thus it made more sense to go with a Speed Density tune.

Here you can see the different custom operating system available for our Camaro. We selected the 3-bar speed density OS with RTT (real-time tuning). This will cost you additional credits (up to 5) so be prepared for that. Upgrading is simply a mouse away.

Converting to a Speed Density operating system (OS) is accomplished by selecting “OS” in the top bar and then selecting one of the custom operating systems that is presented to you. We chose the 3-bar operating system with real-time tuning. This will allow us to run up to 30 pounds of boost and enable us to change the parameters of our tune while the car is running.

You want to make sure that you’ve installed the proper MAP sensor as well. If it is not a 3-bar sensor – one that matches the custom operating system you just chose – global fueling will be severely affected. Once you have upgraded to the new COS (custom operating system), you’ll want to head straight to your Volumetric Efficiency table. This table is responsible for the fueling of the engine. In essence, at least in a Gen III computer, you are telling the computer how efficient the engine is at a given RPM and MAP reading (this is provided in a number from 0 to 100 and can go over 100 percent efficiency with boost or in an extremely efficient naturally aspirated configuration), that will tell the computer how much air is coming into the engine and it will then make calculations to inject the right amount of fuel for that given point in the map. In early Gen III computers, this is an actual number based on the percentage of how efficient the engine is, in later Gen III and Gen IV computers, this is a virtual VE table with much higher numbers that are not directly related to the percentage of efficiency.

Here we see the Volumetric Efficiency table for our Camaro. This table has already been tweaked somewhat to get the fueling values dialed in, but it still has a long way to go.

After converting to the COS, you’ll notice that all your values have been changed to 519 or you now have multiple VE tables. In our case, we had a new expanded table with the maximum values entered for us. The maximum value is added to prevent any damage from running lean, but it will also mean your car cannot start with the table currently like it is. You’ll want to go back to your stock tune file (or naturally aspirated in our case) and copy the VE table up to 105 kPa and paste it into your new custom operating system so that you can start the car.

If you have a cam, as our Camaro does, there are additional changes you’ll want to make in the idle areas of the MAP. You’ll want to decrease the efficiency in these areas since a large cam typically decreases volumetric efficiency at lower RPM and increases it in the higher range. You can reach the VE table by selecting “Engine” in the top bar, then “Airflow,” then “Primary” under the “Main VE” portion. However, if your car was already properly tuned before the addition of a power adder, you’ll have to change a lot less. In our case, we changed virtually everything and must start from scratch with our VE table and other settings.

Making Changes

Now that we’ve upgraded the operating system and got the VE table somewhat sorted, we wanted to tell the computer that it was working with more cubic inches. We did this by going to the “General” tab and first choosing “OHV 6.0L” from the drop-down menu under “Engine” and “Type.” We then must do a quick calculation. The actual displacement of our 370 is closer to 6.1 liters now, so under “Size” and just below “Cylinder” we will give it the correct cylinder volume. This is just 370 cubic inches divided by eight which provides us with 46.25. Don’t be alarmed if the software changes the value somewhat as the hexadecimal code the operating system is built on can only represent specific values and may change it. If it’s close, it will work.

Here you can see that you can select the engine size from the drop-down menu next to “Type.” We also need to change the value for Cylinder Volume which we get by dividing 370, the size of our engine, by eight to come up with the cylinder volume.

With our VE table changed for the time being, and the computer informed that we are working with more cubic inches, it was time to tell it that we switched out the injectors as well. To do this, we headed to the “Fuel” tab and “General.” Here we modified the “Flow Rate,” “Offset,” and “Short Pulse Adder” with the data provided with our Fuel Injector Clinic 1,000cc injectors.

In this table, we adjust for the larger Fuel Injector Clinic injectors. Luckily for us, FIC provides the data for the injectors and it simply needed to be input into three different tables. Once that was all done, we were ready to move on.

The next step in getting Corn Star ready to run was to make sure the MAF was set to fail (essentially turned off) so that it wouldn’t interfere with our VE calculations. Then we set up an air-fuel ratio error histogram so that we could make adjustments to our VE table based on what our wideband was telling us. We will also need to adjust our Power Enrichment tables, but more on that later.

On the left, you can see where we shut off the DTC codes and set our MAF to fail after just one attempt to read. This effectively takes the MAF out of the equation officially making our car speed density. On the right, the frequency at which the MAF is set to fail is 0 hertz.

To make sure the MAF was set to fail every time we start the car, we headed over to the “Airflow” portion of our tune. Under the “Engine Diag” tab in the upper row, we found the “Airflow” tab. Then, under “Mass Airflow Sensor” in the “MAF Frequency Fail High” field, we set the value to 0. Once that’s done, we need to change some of the DTC codes so that we don’t get a check engine light every time we fire up the car. For that, we stayed in the engine diagnostics tab but then select “DTC.” Then we located P0101, P0102, and P0103. In the drop-down box next to each code, we selected “Fail on first DTC” this ensures that when the MAF is found to fail above 0 hertz, the value we set earlier, it will trigger a check engine light and disable the MAF. However, we then uncheck each code so that it will no longer trigger a check engine light.

Here is where we made the adjustments to our boost enrichment table. This table is essential, especially in turbo vehicles. Turbocharged vehicles frequently make boost are partial throttle and low RPM. Since standard power enrichment uses engine RPM, you could be in boost without power enrichment kicking in. This would be a disastrous event for any boosted vehicle.

After we had the car ready for Speed Density, we headed over to our power enrichment table. This is the table that tells the car what air-fuel ratio to shoot for when certain conditions are met. Think of it somewhat like an accelerator pump in a carburetor. Since we don’t want to melt our new build down, we changed the values under both power enrichment tables to 1.278 and 1.28 respectively. This will ensure the computer always chooses the richer of the two which is the boost ratio. But just because that’s what the computer will be striving for now when all of our conditions are met, doesn’t mean it can do it on its own. For that, we set up an air-fuel ratio error histogram.

Ready, Aim, Fire

With our wideband set up in the scanning software and our air-fuel ratio error histogram ready, we were all set to fire our car up and start dialing in our idle and partial throttle fueling via our VE table. But before we did that, we made sure to go into the timing tables and pull the timing for any area that we may see boost. This is to ensure safety, and we will then walk our timing in once we have the car on the dyno. We set our timing map in any power region to just 12 degrees, ensuring we wouldn’t hurt the motor right out of the gate, though E85 is much more forgiving in these circumstances due to its intrinsic low-detonation qualities.

With everything all set, we were ready to fire her up. After a couple of cranks, Corn Star sprung to life and ran well right out of the box. We made a few adjustments to fueling and timing to get it idling a little smoother and after heat cycling it several times; we conducted some partial throttle testing to dial in our VE table a little further. Once we were satisfied that everything was safe, we also did a couple of power runs on low boost to see how close we were on our boost numbers in the VE table. We had to take quite a bit of fuel out of those.

With our base tune uploaded, Project Corn Star was breathing fire.

However, thanks to our previous tune, the car runs and idles pretty good already. There was a needed adjustment to the “Rolling Idle” table to keep the car from stalling on sudden deceleration (a problem it previously had anyways), but once that was taken care of the car was ready to hit the dyno! Something we have been waiting a long time to do.

As we mentioned before, we didn’t cover every step we took or every table we modified, but we’ve shown you here what it took to get Project Corn Star up and running on a Speed Density tune and ready to hit the dyno. The Tuning School’s basic and advanced guides were invaluable in making it all happen, and we highly suggest picking up a copy if you are attempting to do the same. While tuning is not rocket science, it’s the closest we have ever come to something that felt like it, but the guys at The Tuning School lay it all out for you.

With Corn Star officially mobile, we were off to the dyno to turn up the boost, add in some timing, and see what this street beast can make at the tire once and for all. Stay “tuned” as we find out just what kind of power Corn Star can muster in our next installment.

Article Sources

About the author

Chase Christensen

Chase Christensen hails from Salt Lake City, and grew up around high-performance GM vehicles. He took possession of his very first F-body— an ’86 Trans Am— at the age of 13 and has been wrenching ever since.
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